In the related art, as a depressurization device that is applied to a vapor compression refrigeration cycle device, an ejector has been known. In this kind of ejector, a nozzle portion that depressurizes a refrigerant is provided, a gas-phase refrigerant that has flowed out from an evaporator is drawn by suction of a refrigerant sprayed from the nozzle portion, and the sprayed refrigerant and the drawn refrigerant are mixed so as to be pressurized by a pressure increase part (diffuser portion).
Accordingly, in a refrigeration cycle device (hereinafter, referred to as an ejector type refrigeration cycle) including an ejector as a depressurization device, power consumption of a compressor can be decreased using refrigerant pressure action in the pressure increase part of an ejector, and a coefficient of performance (COP) of a cycle can be further improved to a greater extent than a general refrigeration cycle device including an expansion valve or the like as a depressurization device.
In PTL 1, as an ejector applied to an ejector type refrigeration cycle, an ejector including a nozzle portion that depressurizes a refrigerant in two steps is disclosed. More specifically, in the ejector of PTL 1, a refrigerant in a high-pressure liquid phase state is depressurized by a first nozzle until the refrigerant reaches a gas-liquid two phase state, and the refrigerant in the gas-liquid two phase state flows into a second nozzle.
Accordingly, in the ejector of PTL 1, boiling of a refrigerant in the second nozzle is promoted, nozzle efficiency of the entire nozzle portion is improved, and in the entire ejector type refrigeration cycle, COP is further improved.
In a general ejector, a diffuser portion (pressure increase part) is coaxially disposed on an extension line in an axial direction of a nozzle portion. PTL 2 discloses that ejector efficiency can be improved by relatively decreasing the spreading angle of the diffuser portion disposed as described above.
The nozzle efficiency means energy conversion efficiency when the pressure energy of a refrigerant in a nozzle portion is converted into kinetic energy, and ejector efficiency means energy conversion efficiency in the entire ejector.